Signaling system



Y Feb. 20, 1940. c. w. HANsELL SIGNALING SYSTEM Original' Filed March 26, 1931 3 Sheets-Sheet l m h 1 :um il :N J. -am z \N\ Q m m w v m d Q QS m Qu .WSW un www m m w. m wm@ www n m @hm S .m n wbmw GS Ew s Q m m Q m "w m .5 r 45 m l- L. I. IL IL L Jr@ @Q2 l. u FEM n r im. NN I I H N Q k o v N E QN/ R\ wkkm. @ENQ Feb. 20, 1940. c. w. HANsl-:LL

SIGNALING SYSTEM original Pfiled March 2e, 1931 s sheets-sheet 2 INVENTOR- CLARENCE? BY ANSELL ma; TTORNEY- Feb.l 2(1), 1940.

C. W. HANSELL SIGNALING SYSTEM l Original Filed March 26, 1931 5 Sheets-Sheet 3 INVENTOR- CLARENCE W. HANSELL P* JWM `lara-,imma Febgao, 1940 ,i

Clarence W. HansellgPort Jefferson, N. Y., assignor to Radio Corporation of America, a corpora tion ofzDelaware` Original application March26, 1931, Serial No. 525,419, now Patent No. 2,032,208,'dated February 425, 1936. Divided and this application December 30, 1932,Serial No. 649,470

12 claims. (01.,250-1?)` It has been common practice prior to `mypresent invention to controlthe frequency of radio `frequency,transmitters by means of relatively low power, lightly loaded master oscillationathe outputs of which were amplified through aichain of radiofrequency amplifiers to-the power desired `for` transmission. `In this previously developed system the conditions for holdingthe `frequency of themaster oscillators constant couldbe ob- "tainedmore `easily and economicallyvthan would be the case if the oscillations were vdeveloped directly in the vacuumtubes which producethe q power to be radiated from antennae.

A system of the latter kind `has been `developed for high frequencies by the British Marconi Company and iskrlown asthe British Beam System. i l

In the United States a method for maintain- `ing master oscillatorsmuch more constant in frequency than had been possible previously Was invented by W. G. Cady and is disclosed in his United" States Patent 1,472,583; This method of Cadys` employs a piezo-electric crystal and re- "sults in a great improvement in frequency coni trol-` `However,` it is subject to limitations in that its constancy` is diminished at l. the higher frequencies and the amount of power` obtainable l from the crystal oscillator is small.

J frequency multipliers. A method for doing this is` The first limitation is removed by 'operating the crystal oscillator at relatively low frequency and increasing this "frequencyby `vacuum tube i disclosed in U. S. Patent 1,771,375 of I. F. Byrnes. Aft the beginning of the development of high frel put frequency of the transmitter wasmuch highf er than any previously used for high power, long distance, communication.

L In this type of .transmitter the frequency multipliers were all low power tubes of thesame size and type so that there was no increase of power in the successive frequency multiplier stages.

The output from the lastfrequency multipler was amplified by a chain of vacuum `tube amplifiers, allroperating at the samefrequencyyto ythe final power levelrequired for the antenna. In this case the amplifying system followed the previously established practice used in master oscillatoramplier transmitters of `the type lfused inthe claimed `in my copending` application Serial No.

` fore approached in an amplifier system for high British Beam System. The main difference was that the conventional master oscillator was replaced by the combined crystal `oscillator and frequency multipliers.

` Although this method ofconstructing and operating `a transmitter was an improvement over any previously,` used methods, yet, at `high frequencies,` the circulating currents through the dielectric capacities of the tubes `caused losses Whichreduced the amplification and troubles were experiencedy from undesired spurious oscillations. These,` spurious orparasitic oscillations were caused by'` energy feedback from output to input circuits ofamplierstages and from high power stages to lower power stages. The adjustments required to eliminate these undesired oscillations were critical at high frequencies and dimcult to maintain over long periods.

, In accordance with my invention disclosed and l 525,419, filed March 26, 1981, Patent No. 2,032,208, February .25, 1936, of which the present applicai tion is a division, I eliminate most of thelow power frequency multiplying stages and by thev use of a new system in which the successive intermediate stages of amplification Work at successively higher power levels, and, most important, the amplier stages actas frequency multipliers. Thus insaid application, I combine amplification i and frequency .multiplication in the successive stages of an amplifier system. i i l Afterthis is done the earlier stages of the amplifier work at lower frequencies where they are more efficient. `Also in the system disclosed in said application the input andoutput circuitsof 3'5 each intermediate amplifier stage are tuned to different frequencies so that the Afeedbackhfrom output to input circuits causes little current in the input circuit because of its `lach of tuning tothe frequency of the energy fed back.` `Likeo wise the feedback of radiofrequency energy from any `stage'of amplifier toprevious stages is very greatly reduced because `of the wide differences in frequencies to which the amplifier circuits are l tuned.,` Consequently, there is a marked freedom l' from parasitic oscillations andan ease of control and operation borne out intransmittersactually built incorporating the said invention never beradio frequencies. i

` In the said system of frequency multiplication at increasing power and also in the system of frequency multiplication at substantially constant power, I` have obtained a still further-improvemilt nyoperation by the `use `of capacity neu- 55 more than three electrodes may be used in fren 1 quency multiplier-amplifiers to excellent advantage. Transmitters are now in use employing tubes with two grids in which one grid serves'to shield the control grid from the anode and, the addition of the screen grid, which .may be kept substantially at Zero radio frequency potential, together `with appropriate circuit shielding, serves4 some of the purposes ofthe capacity neutralization in my, application Serial No. 177,505

with the advantage. that no :neutralizing adjustment need be made` by an operator'and the probability of ineiciencydue to human error is greatly reduced.

Inthe systemof application Serial o. 525,419,v

it is possible toluse any'or all stages of amplifier as frequency multipliers but ,where expediency in design makes it desirable, `sortie stages :may be used as amplifiers without change of frequency. Preferably, the last stage isan ordinary amplifier since the lastr stage amplifier determines the nal transmitter output so that it is important tofobtain as much` power as possible from git. This is desirable because the power efficiency of the last stage is a. large factor in determining the overall efficiency of the transmitter, and, if the last stage were used as a frequency multiplier it `Would. be necessary to make some sacriiiceA in power output` and'emciency. In said system `l'. employ screen grid` tubes in the last stagev or three *electrode tubeswith capacity neutralization together with .otherfffeatures essential to good 'electrical and. mechanical construction. Under certain conditions Aone or more of the earlier vstages may act as1 ampliers Without .frequency multiplication. For example, I may use an ordinaryampliiier immediately after the crystal because by doing sotheload onthe crystal circuit is reduced Ainsuring greater constancy .of lfrequency.y n

` yIn :the system disclosed in application Serial No. 525,419, I ,improve ithe stability. of loperation of vacuum vtube amplier and frequency multiplier systems to make them less subjectto the effectsofpower supply voltage variations and at the Sametime I protectthe vacuum tubes from destructive currents. `This is accomplisllfied by employing the combination, for electron dis- 'chargedevicea of a xed biasing potential and a potential 'obtained by passing rectified gridcur rent through a grid leak resistance.

It is characteristic of vacuum tube frequency'v multipliers and higheinciency ampliers that the relative Values of grid bias and radio frequency.

i, closed in said ccpending application, I may make thebiasing potential increase and decrease in `accordancel with the excitation in a manner to hold relatively constant output and eiciency' by employinggrid leak bias.

However, when this is done, if for any reason the-master oscillator, or any intermediate stage fails to function, so that there is no excitation on any stages, their grid bias falls to zero. this case the tubes are subject to excessively high and destructive anode currents and losses Which endanger thelives of the tubes. Overload'protection on the power supply will not'fentirely remove this danger because the input currents,

`controlling overload vprotective devices, underv this condition may not exceed the normal input while the energy dissipation in the tubes is greatly increased due to loss of output. In cases where the input currents would be suficiently higherthan normal to trip out overload circuit breakers therejisJstill ldanger of tube failure because the overload, although of shorter duration, is increased in severity.

stillretainingmost of the advantages of grid leak bias, was `a further object of the system disclosed,

i napplcaton Serial NO. 525,419 and t fuljll it I employ sumcient iixedbias rto vprotect the tubesin caseftheir excitationrfails and obtain the remainder of the required ,biasing` potential from grid leak resistances in series vwith the fixed bias.

Ink-practice it is desirable that provision be made whereby a stage or several stages may operateeither `as anamplifler or a frequency multiplier `or lasampIiiers or frequency multipliers'. This permits signaling at diiferent powersand diiferent frequencies with thefsar'ne number iof stagesv and same apparatus.k l

In accordance with thepresent invention I pro-- vide switching and tuning means in the output circuits of certain stages to make them operate as ampliers or frequency multipliers. When they operate as amplifiers the'switching means is set at such a point that the output circuitof the stage isv tuned to the frequency of the input circuit. ."I'hefstager now acts as an amplifier of the impressed oscillations. f

When it is desired thatv the stage act asa frequencyy multiplier `the switching means is set lat such a position that the output circuit of the par To remove thisrdanger yof tube failure while irc ticular stageis tuned to a harmonicA (odd or even) of the frequency to which the input circuit of the stage is tuned. `The stagenovv acts as a fre- `operates efliciently as a frequency multiplier.

' In my novel transmitter of the present invention I provide ymeans for increasingther bias applied to the vcontrol electrodes of the stage when the stage operates as a frequency multiplier, and for decreasing said bias if the stage Ais to be' changed back to a straight amplier or relay. Y

Transmitters including' the novel features of the present kinvention have been in commercial Service for some time. A transmitter including the switching and tuning means as 'disclosed briefly above have been disclosed in my United States application Serial No. 189,162, filed May 5, 1927, Patent'No. 2,063,248, vDecember 8, 1936.

In accordance with United States Patent Oice l proceduremyinven'tionis defined in the appended claims. However, it may best be understood,-both as vtoits Ystructural `organization and mode of operation by referring to the accompanying drawings, wherein: k

j Figure 1 is a block diagram of a commercial transmitter built in accordance withmy present invention; while,

IFiguresv 2,; 2a and 2o schematically illustrate ya circuit arrangement used inthe apparatus shown in Figure 1.

buffer or shock absorbing amplifier 4, two frequency multiplier stages B, 8 the latter also being used as a modulator and both multipliers being used preferably as frequency doublers. Another stage I0 adapted to be used as a simple amplifier or, as indicated, as a frequency tripler, and, a nal amplifier stage I2 are provided. As indicated, the crystal controlled oscillator 2, buffer amplifier 4, and first frequency multiplier 6, may be placed safely within a single shielding compartment 5 withoutfear of parasitic oscillation generation, and similarly the stages 8, and lil may be placed in another separate shielding compartment `7. The nal amplifier stage I2 should, ofcourse, be placed with an individual shielded compartment 9. Inasinuch asshielding is Well known in the art,` a further description of it is` unnecessary heren I The tube sizes indicated in Figure 1, are given merely by way of example and as set forth more in detail in my application Serial No.` 525,419 may be varied widely in practice. Attention is directed in particular to the second frequency multiplier and` amplifier 8, which is of much larger size and rating than frequency multiplier and amplifier 6 or, amplifier 4. As a result of `this e construction, a considerable amount of amplification of the energy is produced in the frequency multiplier, which eliminates many of the amplifiers which would be necessary if, in accordance with prior practice, the frequency multipliers are all` made of the same size and rating, such as that of stage 6 for example. And similarly, the frequency multiplier stage ID is made considerably lar-ger in size and ratingthan the prior stage `Il` so that within the frequency multiplier I0 a considerable amount `of amplification ensues along with frequency multiplication. By the use `of amplification within the `stages and I0, as

already indicated, a long chain of amplifiers, subject tlo parasitic oscillation andcostly maintenance, for building up the energy to a value sui- Cient to operate power amplifier l2 is eliminated.

The arrangement shownin Figure 1 is illustrated in greater detail in`Figures 2, `2a andf 2b.

The regeneratively coupled electron discharge dei vice oscillator 2` is frequency controlled byeither crystal I4 or I6 by suitable actuation of coupling or switching arrangement l I which couples either crystal capacitively to the input electrodes of oscillator 2. The purpose of using two crystals is, of course, to provide a spare crystal or to vary the final output of the transmitter.

The crystals preferably are temperature controlled by any suitable temperature controlling indicated Within heating energy from condenser i3 to the louier amplifier 4 having a tunable output circuit I9 tuned also to substantially the fundamental frequency. To prevent parasitic oscillation generation or self oscillation, the buffer `oscillator may be neutralized by the `use of a suitable neutralizing condenser 20 as indicated, or, as illustrated in my application Serial No. 525,419 the transmitter tubes may be made of the screen grid type so that external neutralizing circuits are unnecessary. Similarly, for better control the crystal oscillator tube lmay be of the screen grid type or of any multi-electrode type. Th'buffer amplifier, of course, acts to maintain constant load on the crystal oscillator preventing variations in load from making themselves felt upon the electrodes of the `oscillator 2.

Output `energy appearing in tunable circuit IS March 23, 1927,` frequency multiplier and `amplii iier 6 may be regeneratvely coupled by means` of a condenser 2| for energy of harmonic frequencies, but degeneratively coupled for energy u of the fundamental frequency so that presenceof energy of the fundamentalfrequency in theoutput circuit of tube B is effectively eliminated or reduced to a negligible value. i i

Heating current for the electron emission elementsv of the tubes 2., 4 and Bmay be supplied from a 60 cycle source as shown. Positive potential for the anodes of tubes2, 4 and 6 may be supplied by Wave of leads b, while biasing potentials for` the control grids of tubes 2, 4 and i5 may be` supplied` by way of leads c from any source.

Output energy from the frequency doubler 6 and amplifierl is fed through conductor a to the frequency multiplier-amplifier modulator'S shown in Figure 201,. The output circuit of tube 8 lis tuned substantially to the fourth harmonic of `the.fundamental and as illustrated is regeneratively connected by capacity 21 for energy of the harmonic frequency 4f.

Keyed energy appearing in lines 22 may bev used to remotely control the electromechanical relay 24 to alter thebias on the grid of tube Il so `that when the relay armature is in its contacting position it `will shift the grid voltage on tube 8 to `such a value as to pass peaks of input current into the output circuit of tube 8 such that it is shock` excited at the harmonic frequency 4f as described more fully in my appending application just referred to. position of relay 24, a less negative potential is supplied by way of conductor 2li coupled to a suitable point on `potentiometer 28, and key 23 closed in the left hand position, to the grid of tube` 8 through connections 30. When the relay armature is in tlieopen position, negative tapping point 32 biases the grid of tube 8 through resistance 34 to such an` extent that no high frequency energy appears in the output circuit 36 of tube 8. in addition to the relay for controlling the transmitter there is provided means by which the control may be transferred from relay 24 to the local telegraph key 25 for the use of the trans-` mitter attendant. To do` so switch 23 is closed in the righthand position.

Fourth harmonic signal modulated high frequency energy is fed inductively, as indicated, throughlines 3B tothe inputelectrodes of a pushpull connectedffrequency amplifier or frequency multiplier and ampluier I llffor` the. completer action of which reference is again made to my cepending application Serial No; 177,505. As shown, the stage l 0 acts simply as an amplifier, but, this stage may be used as a `frequency multiplier to produce energy of a frequency three times the frequency of the energy appearing in the input circuit 40. The energy thus produced is of a frequency I2f.

With the switches 42 and 44 in the position shown the tuned resonate output circuit connected with the stage I8 includes the inductances 52, 54 and 60 and the variable capacities 56 and 58 which tunes said circuit to the frequency of the input circuit 40, that is, to a frequency 4f. `The tubes now act as simple amplifiers.

When switches 42, 44 are moved to thei other position by uni-control means 46, 44 closes contact 44'so that a higher negative bias is applied to the grids of the pushpull connected tubes Hl by way of lead 31 from the potentiometer 43 connected with any source. The same movement of .control means 46 closes contacts 45 so that the portion of the output circuit 48 to the right of the dotted line5, is cut out of circuit entirely, or is short-circuited away from" the output electrodes of tubes I8. switch, the output circuit includes inductances 52, 54 and condenser 56, and these elements tune said circuit to the twelfth harmonic of the fundamental 4f as indicated.

In both positions of the switches the circuits of the pushpull` stage are symmetrical as shown. In both positions of the switches potential is supplied to the anodes of` the tubes in stage lil by vway of a lead 41 to the electrical center ofthe resonate output circuit. When the stage acts as an amplifier the inductance 49 is included in this connection.

fio.

When acting as a simple amplifier, output energy 'from the output circuit of tubes l is fed through blocking condensers 82 and lines t4 to theinput sideI of the power amplifier l2. When acting as a frequency tripler or multiplier as indicated, output energy from tubesv I 0 is fed inductively by secondary coil 66, to the lines 58 throughblocking condensers 1D andl to the input .always used, in order to obtain best overall eiliciency for the entire transmitter, as a simple amplifier, provision being made to readily adjust the tuning of the amplifier to either one of the frequencies which it is desired to amplify. Thus, a uni-control switching means 72 is provided which places low frequency coils 88 and 82 in the input and output circuits respectively of tubes l2, when stage lI!) is used as an amplifier for energy of the lower frequency 4f. Under such circumstances also, the transmission line H8 to the short wave or high frequencyv antenna is grounded by switches 88 as indicated. The' long wave antenna 86 is connected by switches 88,

as shown, to the long wave output circuit inciuding 82. i f f A reverse movement of controlling member 'l2 will act to short-circuit the long wave coil 82 out of circuit by switch 84, to connect the low wave length antennav transmission line VVin circuit at In this latter position of switch 8U and, ther'elatively longer wave antenna transmission line 86 will be grounded by the other position `of switches 88. In the input circuit, the longer wave coil 80 will be removed from circuit, and, the shorter wave coil 'i4 will be placed inthe circuit, all of which takes place on the reverse setting of switch 12.

This uni-control arrangement for rapid changeover in amplier frequency is broadly similar to that described and claimed in my copending-application Serial No. 189,162, filed May 5, 1927.

To prevent parasitic oscillation generation, the power amplifier tubes I2 areneutralized by condensers 94 cross-connecting the terminals of the input and output tuning condensers 95, 98 respectively.

As indicated, the cathodes of the various tubes Vmay be energized by alternating currents. Unidirectional potentials for. the potentiometers 28 and 43 and the various unidirectional supply leads b and cshown in Figures 2, 2a and 2o may be obtained from separate rectiers as found necessary, but, in accordance with the present invention it is preferred that the separate rectiersv be energized from a single alternating current source whereby there is less tendency for changes in amplification with changes in supplied alternating voltages as would be the case where various rectiers are supplied from different alternating sources.

I claim:

1. In a high frequency transmitting system employing thermionic tubes, a circuit for impressing on the input electrodes of said tubes a characteristic control frequency, a symmetrical compound output circuit connected between the anodes of said tubes, said compound' circuits including two sections, each section having lumped inductances and capacities connected in parallel, switching means associated with said output circuit for short-circuiting one of said sections to change the resonance frequency of said circuit, and meanscooperating with said switching means for maintaining symmetry of said output circuit in all positions of said switching means.

2. Relaying means comprising, a pair of thermionic tubes, each having control grid, anode and cathode electrodes, a tuned circuit connected between the control grids of said tubes, a pair of signal resonant circuits comprising series inductances and parallel capacities, one of which circuits includes the other, connected between the anodes of said tubes, switching means including a switch for short-circuiting a portion cf said output circuit, and inductive means connected to-the electrical center of said circuit and cooperating with said switching means for maintaining said output circuit symmetrical in all positions of said switch.

3. Relaying means comprising, a pair of thermionic tubes, each having control grid, anode and cathode electrodes, a signal resonate circuit connectedin phase opposition between the control grids of said tubes, a circuit including several inductances in series and capacities each shunting one or more of said inductances connected in phase opposition between the anodes of said tubes, switching means including a switch in parallel with one or more of said capacities and inductances, said switch in the open position permitting said circuit to resonate at one frequency and in the closed position at a different frequency andmeanscooperating with said switching means for maintaining said output circuit symmetrical in `all positions of said switch.`

4. Signaling means comprising, a pair of thermionic tubes, each having control grid, anode and cathode electrodes, means for operating said tubes as amplifiers or frequency multipliers comi circuit to tune said circuit to the fundamental frequency or to include a lesser number of said impedances and capacities in said circuit to tune said circuit to a multiple of said fundamental frequency.

5. Signaling means as recited in claim 4 in which an inductance cooperates with said switching means to `maintain said output circuit symmetrical in al1 positions of said switch.

6. `Signaling means as recited in claim 4 in which a second switch cooperates with a source of potential to apply different values of biasing potential to the control grids of said tubes in different positions of said first named switch.

7. `A relaying device comprising, a pair of thermionic tubes, each having anode, cathode and control grid electrodes, a tuned `circuit connected between the control grid electrodes of said tubes, a source of biasing potential, switching means for applying bias potentials of different values to the control grid electrodes of said tubes, an output circuit` including tuning means connected between. the anode electrodes of said tubes, switching means cooperating therewith in such a manner that in one position of said switch said output circuit is resonant at the frequency to which the input circuit is tuned and in another `posi-- tion of said switch the output circuit is resonant to a frequency which is a multiple of the frevquency of the input circuit, a single control means for both of said switching means, and means for maintaining a point intermediate the terminals of said output circuit at a radio frequency potential substantially equivalent to the radio frequency potential of the cathodes of said tubes.

8. A relaying device comprising, a pair of thermionic tubes,` each having anode, and control grid electrodes, a tuned circuit connected between the control grid electro-des of said tubes, a source of biasing potential, a circuit and switching means for applying like potentials of different values to the control grid electrodes of said tubes in different positions of said switch, an output circuit including symmetrical sets of impedances, switching means for connecting one or more sets of saidirnpedances to the anodes of said tubes in such a manner that in one position of said switch said output circuit is resonant at the frequency to which the input circuit istuned and in another position of said switch the output circuit is resonant to a frequency which is a multiple of the frequency of the input circuit, and a single control means for both of said switching l means.

9. A relaycomprisng, a thermionic tube having an anode, a cathode and a control electrode, a circuit for applying a biasing potential to the control electrode of said tube, and means for opactances tuning saidy circuit to resonance at the control frequency, whereby said relay acts as an amplifier, and means for cutting out of circuit orshort-circuiting selected ones of said capacitive `and inductive reactances, whereby said output circuit is resonant toI a frequency which i y a multiple of the control frequency.

10. A relay as recited in claim 9 including means for increasing the biasing potential applied to the` control electrode of said tube when the reactance in said output circuit is decreased.

11. A relay as recited in claim 9 including means for changing the biasing potential applied to the control electrode of said tube when the reactance in said output circuit is changed.

12. lin a high frequency transmitting system employing thermionic `tubes in a symmetrical circuit arrangement, a circuit for limpressing on the control grids of said tubesa control frequency, an output circuit connected between the anodes of said tubes, said output circuit comprising several inductive reactive portions adapted to tune said output circuit to the control frequency or a multiple thereof switching` circuits `connected with said output circuit `for selectively removing selected onesof said portions from said output circuit for changing the tuning of said output circuit, and `a circuit` cooperating with` said switching means for maintaining symmetry of said output circuit in all positions of said switching means, f i

i CLARENCE W. HANSELL. 

